Thanks Michael the explanation is great - with MOIv5 the fillet 3d shape engine is now controlled by acis is the plan to roll it out to the curve based filleting also and will this improve anything on that side? Here is what I am trying achieve - with the tube bending software it reads the fillets in the solid to gauge a change in direction for the pipe to bend I am finding if I make radius small it still works i can override the radius info in the cam software and apply the correct tooling radius which then corrects everything for bending. All the best Alex.